<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>盒模型的小demo</title>
    <style>
        input {
            box-sizing: border-box;
            padding-left: 40px;
            width: 400px;
            height: 50px;
            background-color: #5c88d0;
            border: 0;
            border-radius: 40px;
            outline: none;
        }
    </style>
</head>
<body>
    <input type="text" name="" id="" placeholder="请输入手机号码">
</body>
</html>